The purpose of this study is to investigate the possible efficacy and safety of new compounds for the treatment of certain disorders of movement, and to employ drugs as tools to analyze the physiological and pharmacological mechanisms mediating various motor deficits. The main conclusions deriving from observations over the last year are: (1) The neurological deficits of Parkinsonism stem, at least in part, from inadequate transmission of D-2 receptors, which can be alleviated by selective D-2 agonists. (2) Lisuride has antiparkinson efficacy, with adverse actions similar to bromocriptine but more prominent induction of somnolence. (3) Administration of carboxyl labelled levodopa is a convenient approach to monitoring dopamine formation in Parkinsonian patients. (4) Dopaminergic systems outside the nigrostriatal pathway are abnormal in Parkinson's disease; there is increased sensitivity of D-2 receptors on lactotroph cells in the pituitary. (5) The programming of voluntary movement appears to be normal in Parkinson's disease. (6) The relationship between voluntary and postural motor mechanisms is normal in Parkinson's disease. (7) The capillaries forming the blood-brain barrier of the substantia nigra are less susceptible to chemical damage than those of the cerebral cortex and striatum.